1. Field of the Invention
The present invention relates to an image processing method, and more particularly, to a deinterlacing device and method capable of converting interlace field image data into a progressive frame image data.
2. Discussion of Related Art
Interlacing image data is displayed on one frame of screen composed of two fields, i.e., an odd field and an even field, as shown in FIG. 1.
However, some types of displays do not process the interlacing image data but they process a progressive image data which is used on a monitor of a computer, instead. In this case, there is a need to install an additional system for converting the interlacing image data into the progressive image data in the interior of the display.
A method for converting the interlacing image data into the progressive image data is embodied in various ways, as shown in FIGS. 2a to 2c. 
As to a line repetition method, as shown in FIG. 2a, one frame is made in such a manner that the line information of a current field is simply repeated. The line repetition method is realized with a simple hardware but has a defect that a quality of image is deteriorated after interpolation.
As to an inter-field interpolation without motion-compensation method, as shown in FIG. 2b, one frame is made in such a manner that a previous field line is inserted between current field lines. The inter-field interpolation without motion-compensation method is realized with a simple hardware but has a defect that even if the motion image is interpolated, an error is generated or a screen is degraded, thereby causing a quality of image to be deteriorated.
As to an intra-field interpolation, as shown in FIG. 2c, one frame is made in such a manner that into the area between two lines in one field the data made by dividing the two line data into two is inserted. The intra-field interpolation obtains a relatively vivid quality of image when compared with the line repetition method and exhibits a lower error generation than the inter-field interpolation without motion-compensation method. However, it has a defect that after the interpolation of still image, the screen is degraded, thereby causing a quality of image to be deteriorated.
As another interpolation method, there is presented a current screen interpolation method using the field data of a previous screen and the field data of a screen to be displayed. Particularly, this method detects the points where motion occurs on the screen by using four continuous field data on the basis of a current field data and interpolates the current frame screen in accordance with the motion detection result. Generally, the interpolation of the current frame screen is carried out by using two previous field data, the current field data and the next field data. However, in case of the screen where the motion speed is relatively fast when compared with the period of each field to be interpolated, it has a defect that the interpolation is difficult or has been erroneously executed.
As described above, such the conventional methods for converting the interlacing image data into the progressive image data suffer the problem that the quality of image is poor after the interpolation or the interpolation is erroneously executed.
To solve this problem, there are presented a xe2x80x9cBernardxe2x80x9d method disclosed in U.S. Pat. No. 5,027,201 and a xe2x80x9cFaroudjaxe2x80x9d method disclosed in U.S. Pat. No. 5,159,451, which overcome the deterioration of the quality of image after the interpolation. However, these methods suffer a problem that a manufacturing cost of a circuit is expensive due to a plurality of field memories and a relatively complicated procedure.
It is, therefore, an object of the invention to provide a deinterlacing device and method capable of improving a quality of image after interpolation, without having a complicated circuit configuration, at the time when an interlacing screen is converted into a progressive type screen.
It is another object of the invention to provide a deinterlacing device and method capable of interpolating a field screen, based upon picture elements positioned in a diagonal direction to a picture element to be interpolated.
It is still another object of the invention to provide a deinterlacing device and method capable of detecting motion information of a field and carrying out interpolation in accordance with the motion and edge direction.
It is yet another object of the invention to provide a deinterlacing device and method capable of detecting a brightness difference among picture elements positioned on a predetermined area in vicinity of the picture element to be interpolated to thereby carry out the interpolation for a field screen.
According to an aspect of the present invention, there is provided a deinterlacing device comprising: a field memory for storing m continuous field data containing an nth field data and positioned before and after the nth field data on the basis of the nth field data of a plurality of field data for output image; a motion determination part for detecting picture element values and brightness profile pattern difference values in specific lines existing among the field data stored in the field memory to calculate a motion value of a moving picture; a spatial interpolator for calculating a variation direction of picture element values on an area to be interpolated in the nth field data to thereby output a direction value; a time interpolator for averaging the picture element values on the area to be interpolated in a previous field data of the nth field data and the picture element values on the area to be interpolated in a next field data of the nth field data to thereby output the picture element average value; and a soft switch for mixing the direction value outputted from the spatial interpolator and the picture element average value outputted from the time interpolator, based upon the motion value determined in the motion determination part to thereby output the mixed result.
The motion determination part is, preferably, comprised of a brightness difference and brightness profile pattern difference (hereinafter, which is referred simply to BD and BPPD) detector for calculating the brightness difference and the brightness profile pattern difference in the field data and a BD and BPPD combiner for carrying out the mapping to a predetermined set value, if the brightness difference and the brightness profile pattern difference are over a predetermined limit value, to thereby measure the motion value.
The deinterlacing device further comprises a median filter for grouping the motion values calculated in the motion determination part and a motion expander for expanding the motion value from the picture elements having motion on the specific line to adjacent picture elements in accordance with the motion value grouped in the median filter to thereby output the expanded motion value to the soft switch.
The deinterlacing device further comprises a vertical line converter for converting the number of vertical lines on the nth field screen, based upon the output value of the soft switch and the field data values stored in the field memory.
The spatial interpolator detects the edge direction of a picture element to be currently interpolated, based upon the field data values stored in the field memory and averages the picture element values of the adjacent picture elements to the picture element for which the edge direction is detected to thereby determine a picture element value to be interpolated.
According to another aspect of the present invention, there is provided a deinterlacing method comprising the steps of: storing m field data corresponding to an interlacing type broadcasting program image; detecting picture element values on a predetermined area in which a picture element to be interpolated is contained in the field data; detecting a variation direction of the picture element values on the predetermined area; calculating an interpolation value, based upon the variation direction of the picture element values; and interpolating a current field data with the calculated interpolation value.
The step of detecting the variation direction of the picture element values comprises the steps of: detecting picture element values in the vicinity of an edge of a first area in which the picture element to be interpolated is contained; shifting the first area at predetermined intervals to continuously detect the picture element values in the vicinity of the edge shifted; calculating a variation amount of the picture element values continuously detected; and sensing the variation direction of the picture element values, based upon the variation amount of the picture element values.
The step of continuously detecting the picture element values comprises the steps of: setting a first observation window on a part of an upper line of a line in which the picture element to be interpolated is contained and setting a second observation window on a part of a lower line thereof; and shifting the first and second observation windows at predetermined intervals to detect the picture element values on the edge in each observation window.
The step of interpolating the current field data with the calculated interpolation value comprises the steps of: linearly interpolating the picture element value of each picture element contained in a second area in which the picture element to be interpolated is contained between adjacent picture elements; replacing the picture element value interpolated between the adjacent picture elements between the adjacent picture elements; calculating a difference between two arbitrary picture element values in the picture elements within the second area; calculating a minimum value of the difference values; setting an interpolation area in which the two picture elements having the minimum value are contained; and calculating an average value of all picture element values contained in the interpolation area as the interpolation value and interpolating the current field data with the calculated interpolation value.